[Amps] Efficiency of AL-811/Al-811H compared to older amps

[Martin J. Morgenbesser]

Following up on the previous thread about SB-200 and SB-1000 current draw 
at 110 to 120 volts, I've been wondering: What is it about the 
AL-811/AL-811H design that makes that amplifier series so efficient 
compared to older tube amplifiers of similar power output levels?

According to the specs, the AL-811/AL-811H only draws a maximum of 8 amps 
at 120 volts compared to the SB-200 which draws a maximum of 16 amps at 110 
volts. These amps produce comparable output power levels. Does the 
difference have to do with the tube type (811A vs 572B) or the power supply 
components?

Also, is the old Collins 30L-1 4x811A design as efficient as the new AL-811H?

If anyone would know the answers to these questions, it would be the guys 
on this list. Thanks again, in advance, for your replies.

And happy holidays to all!

73 de W7MJM